linux-kernel - [PATCH] rtla/timerlat_bpf: Stop tracing on user latency

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Message-ID: <20251006143100.137255-1-tglozar@redhat.com>
Date: Mon,  6 Oct 2025 16:31:00 +0200
From: Tomas Glozar <tglozar@...hat.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
	John Kacur <jkacur@...hat.com>,
	Luis Goncalves <lgoncalv@...hat.com>,
	Costa Shulyupin <costa.shul@...hat.com>,
	Crystal Wood <crwood@...hat.com>,
	Wander Lairson Costa <wander@...hat.com>,
	Tomas Glozar <tglozar@...hat.com>,
	stable@...r.kernel.org
Subject: [PATCH] rtla/timerlat_bpf: Stop tracing on user latency

rtla-timerlat allows a *thread* latency threshold to be set via the
-T/--thread option. However, the timerlat tracer calls this *total*
latency (stop_tracing_total_us), and stops tracing also when the
return-to-user latency is over the threshold.

Change the behavior of the timerlat BPF program to reflect what the
timerlat tracer is doing, to avoid discrepancy between stopping
collecting data in the BPF program and stopping tracing in the timerlat
tracer.

Cc: stable@...r.kernel.org
Fixes: e34293ddcebd ("rtla/timerlat: Add BPF skeleton to collect samples")
Signed-off-by: Tomas Glozar <tglozar@...hat.com>
---
 tools/tracing/rtla/src/timerlat.bpf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/tracing/rtla/src/timerlat.bpf.c b/tools/tracing/rtla/src/timerlat.bpf.c
index 084cd10c21fc..e2265b5d6491 100644
--- a/tools/tracing/rtla/src/timerlat.bpf.c
+++ b/tools/tracing/rtla/src/timerlat.bpf.c
@@ -148,6 +148,9 @@ int handle_timerlat_sample(struct trace_event_raw_timerlat_sample *tp_args)
 	} else {
 		update_main_hist(&hist_user, bucket);
 		update_summary(&summary_user, latency, bucket);
+
+		if (thread_threshold != 0 && latency_us >= thread_threshold)
+			set_stop_tracing();
 	}
 
 	return 0;
-- 
2.51.0